package cn.com.util;

import java.util.Random;
import java.util.UUID;

public class UUIDUtil {

	public static final String allChar = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String letterChar = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	public static final String numberChar = "0123456789";

	/**
	 * 由大小写字母、数字组成的随机字符串
	 * 
	 * @param length
	 * @return
	 */
	public static String generateString(int length) {
		StringBuffer sb = new StringBuffer();
		Random random = new Random();
		for (int i = 0; i < length; i++) {
			sb.append(allChar.charAt(random.nextInt(allChar.length())));
		}
		return sb.toString();
	}

	/**
	 * 由大小写字母组成的随机字符串
	 * 
	 * @param length
	 * @return
	 */
	public static String generateMixString(int length) {
		StringBuffer sb = new StringBuffer();
		Random random = new Random();
		for (int i = 0; i < length; i++) {
			sb.append(letterChar.charAt(random.nextInt(letterChar.length())));
		}
		return sb.toString();
	}

	/**
	 * 由小字字母组成的随机字符串
	 * 
	 * @param length
	 * @return
	 */
	public static String generateLowerString(int length) {
		return generateMixString(length).toLowerCase();
	}

	/**
	 * 由大写字母组成的随机字符串
	 * 
	 * @param length
	 * @return
	 */
	public static String generateUpperString(int length) {
		return generateMixString(length).toUpperCase();
	}

	/**
	 * 产生指字个数的0组成的字符串
	 * 
	 * @param length
	 * @return
	 */
	public static String generateZeroString(int length) {
		StringBuffer sb = new StringBuffer();
		for (int i = 0; i < length; i++) {
			sb.append('0');
		}
		return sb.toString();
	}

	/**
	 * 将数字转化成指字长度的字符串
	 * 
	 * @param num
	 * @param fixdlenth
	 * @return
	 */
	public static String toFixdLengthString(long num, int fixdlenth) {
		StringBuffer sb = new StringBuffer();
		String strNum = String.valueOf(num);
		if (fixdlenth - strNum.length() >= 0) {
			sb.append(generateZeroString(fixdlenth - strNum.length()));
		} else {
			throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth
					+ "的字符串发生异常!");
		}
		sb.append(strNum);
		return sb.toString();
	}

	/**
	 * 将数字转化成指字长度的字符串
	 * 
	 * @param num
	 * @param fixdlenth
	 * @return
	 */
	public static String toFixdLengthString(int num, int fixdlenth) {
		StringBuffer sb = new StringBuffer();
		String strNum = String.valueOf(num);
		if (fixdlenth - strNum.length() >= 0) {
			sb.append(generateZeroString(fixdlenth - strNum.length()));
		} else {
			throw new RuntimeException("将数字" + num + "转化为长度为" + fixdlenth
					+ "的字符串发生异常!");
		}
		sb.append(strNum);
		return sb.toString();
	}

	/**
	 * 这个方法只支持最大长度为32的随机字符串,如要支持更大长度的，可以适当修改此方法，如前面补、后面补，或者多个uuid相连接
	 * 
	 * @param length
	 * @return
	 */
	private static String toFixedLengthStringByUUID(int length) {

		// 也可以通过UUID来随机生成
		UUID uuid = UUID.randomUUID();
		return uuid.toString().replace("-", "").substring(0, length);
	}
}
